If it would be this straightforward, why doesn't Postgres do this directly?
There is the misconception that tuning Postgres is just about the memory and CPUs. It's also a lot about the usage patterns, whether you use or not a connection pooler in front (note: you should), about your OLTP-ish or OLAP-ish pattern, about the disk speed, disk technology, types of queries that you do.... it's, unfortunately, not simple at all.
And the problem is that it's easy to think "oh, even if I get it close to right and maybe improve performance by 20% instead of 50%, that's still ok". But the problem is that a bad tuning may decrease your performance significantly. So it's a matter not to take it lightly.
